As mobile devices have been increasingly developed, and the demand of such mobile devices has increased, the demand of secondary batteries has also sharply increased as an energy source for the mobile devices. Among them is a lithium secondary battery having a high energy density and a high discharge voltage, on which much research has been carried out and which is now commercially available and widely used.
Depending upon the kinds of external devices in which the secondary batteries are used, the secondary batteries may be used in the form of a single battery or in the form of a battery pack having a plurality of unit cells electrically connected with each other. For example, small-sized devices, such as mobile phones, can be operated for a predetermined period of time with the output and the capacity of one battery. On the other hand, a battery pack needs to be used in middle- or large-sized devices, such as laptop computers, power tools, and hybrid electric vehicles, because high output and large capacity are necessary for the middle- or large-sized devices.
The battery pack is a battery structure in which a plurality of unit cells are electrically connected in series and/or in parallel with each other. It is very important to sequentially connect the unit cells in the battery pack. In a conventional battery pack, electrode terminals of the unit cells are generally connected with each other, in a highly cohesive welding or soldering fashion using conductive connection members, such as plates, such that the unit cells are electrically connected with each other. However, the welding or soldering operation is an operation that requires a sophisticated technique, and therefore, it is necessary to secure skilled technicians and a large work space. Especially when physical impacts are applied to the battery cells, electric short circuits may occur in the battery cells, with the result that the battery cells may catch fire or explode, and therefore, the safety of the battery cells is not guaranteed.
Also, the above-described connection structure needs auxiliary members, such as jigs, to stably fix the plates to the electrode terminals of the unit cells, with the result that the manufacturing costs of the battery pack is increased.
Consequently, there is a high necessity for a connection member of a novel structure that can be easily assembled and does not need the use of an additional auxiliary member.